Many types of hot applied glass sealants are currently used in the insulated glass sealant market. One type is a two-component chemically-cured sealant. Another type is a single-component curing sealant. Another type is a non-curing hot melt, butyl rubber based sealant. The present invention is directed towards an improved high performance, non curing, hot melt, window sealant that does not require butyl polymer. This novel sealant is suitable for use as an edge sealant for the manufacture of insulated glass structures.
Two-component sealants irreversibly cure to form solid thermoset elastomeric sealants. In using these sealants, both the ratio of components and their mixing are important and must be precise. If there is any error in the ratio of the components, or if improper mixing occurs, the sealant will not cure properly and/or will not adequately chemically adhere to a substrate. The reaction is irreversible and cannot be terminated. This creates problems if the reaction occurs too slowly or too rapidly while the sealant is being applied or if curing occurs during potential equipment shutdowns. As such, application equipment must be thoroughly purged of mixed sealant or the sealant will cure in the equipment. Purging wastes materials and time, thus adding costs to the final product. Further, if the sealant has not properly cured it does not have the mechanical properties to sufficiently hold the window together. Any premature handling or movement of the window causes premature cohesive failure of the sealant, and/or sealant-to-substrate bond delamination. Also, slow curing of the sealant requires that the window manufacturing facilities have staging areas to allow the sealant to properly cure. This lost time and space results in higher costs.
Single-component curing sealants only slightly reduce the need for post application cure time staging areas and have essentially all of the similar application concerns of the two component materials. The exception for single component cure systems is that the ratio and mixing limitations take place at the sealant manufacturing location rather than at the window manufacturing location. The net effect is that a complication in assuring a finite and effective window seal is achieved. Single-component curing sealants also rely upon a water vapor cure mechanism which requires an effective packaging system to prevent the inclusion of atmospheric moisture. Such packaging is often ineffective and results in inferior product performance due to post application cure.
Butyl rubber-based sealants have none of the cure associated application liabilities. They offer uncomplicated application parameters along with the elimination of cure time window handling requirements. Although somewhat inferior to cross linking systems, industry testing has shown butyl sealants to perform reliably at considerable cost advantage. They have historically shown utility in the competitively priced residential window category. However, butyl polymers have routinely been associated with supply concerns as the raw material feed stocks used to produce the butyl are increasingly directed towards the manufacture of other higher value polymeric materials. As such, butyl rubber manufacture is often constrained and subjected to extreme pricing fluctuations based upon the supply and demand curve. Universally employed in the manufacture of hot applied non curing window sealants, butyl rubber supply has the very real potential to produce a situation whereby an entire product class of non curing window sealants risks being priced out of the marketplace. Such an occurrence will render many window producers within the insulated glass window marketplace without adequate sealant supply.
A new class of non crosslinking hot melt window sealants has now been developed. Prior to the arrival of these newly formulated materials, butyl rubber has defined the non curing window sealant marketplace. Butyl rubber has de facto been required to manufacture a hot melt product intended for use as a sealant for insulated glass window manufacture without otherwise employing a post application cure mechanism. Removal of the butyl rubber from these systems effectively eliminates the associated supply concerns and provides an entirely new design space for formulation of insulated window glass sealant products. These new materials have been formulated to completely eliminate the butyl rubber polymer component, while improving upon resultant insulated glass window sealant performance. The materials have been certified to comply with industry recognized ASTM test methods; E 2188, E2189, and E2190, collectively referred to as HIGS or Harmonized Insulated Glass Standards.